for-5.16-fixes contains two subtle race conditions which were introduced by
scheduler side code cleanups. The branch didn't get pushed out, so merge
into for-5.17.
nr_running is never modified remotely after the schedule callback in
wakeup path is removed.
Rather nr_running is often accessed with other fields in the pool
together, so the cacheline_aligned for nr_running isn't needed.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In unbind_workers(), there are two pool->lock held sections separated
by the code of zapping nr_running. wake_up_worker() needs to be in
pool->lock held section and after zapping nr_running. And zapping
nr_running had to be after schedule() when the local wake up
functionality was in use. Now, the call to schedule() has been removed
along with the local wake up functionality, so the code can be merged
into the same pool->lock held section.
The diffstat shows that it is other code moved down because the diff
tools can not know the meaning of merging lock sections by swapping
two code blocks.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The commit 6d25be5782 ("sched/core, workqueues: Distangle worker
accounting from rq lock") changed the schedule callbacks for workqueue
and moved the schedule callback from the wakeup code to at end of
schedule() in the worker's process context.
It means that the callback wq_worker_running() is guaranteed that
it sees the %WORKER_UNBOUND flag after scheduled since unbind_workers()
is running on the same CPU that all the pool's workers bound to.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Long time before, workers are not ALL bound after CPU_ONLINE, they can
still be running in other CPUs before self rebinding.
But the commit a9ab775bca ("workqueue: directly restore CPU affinity
of workers from CPU_ONLINE") makes rebind_workers() bind them all.
So all workers are on the CPU before the CPU is down.
And the comment in unbind_workers() refers to the workers "which are
still executing works from before the last CPU down" is outdated.
Just removed it.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The commit 6d25be5782 ("sched/core, workqueues: Distangle worker
accounting from rq lock") changed the schedule callbacks for workqueue
and removed the local-wake-up functionality.
Now the wakingup of workers is done by normal fashion and workers not
yet migrated to the specific CPU in concurrency managed pool can also
be woken up by workers that already bound to the specific cpu now.
So this advanced kicking of the idle workers to migrate them to the
associated CPU is unneeded now.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull networking fixes from Jakub Kicinski:
"Including fixes from bpf, can and netfilter.
Current release - regressions:
- bpf, sockmap: re-evaluate proto ops when psock is removed from
sockmap
Current release - new code bugs:
- bpf: fix bpf_check_mod_kfunc_call for built-in modules
- ice: fixes for TC classifier offloads
- vrf: don't run conntrack on vrf with !dflt qdisc
Previous releases - regressions:
- bpf: fix the off-by-two error in range markings
- seg6: fix the iif in the IPv6 socket control block
- devlink: fix netns refcount leak in devlink_nl_cmd_reload()
- dsa: mv88e6xxx: fix "don't use PHY_DETECT on internal PHY's"
- dsa: mv88e6xxx: allow use of PHYs on CPU and DSA ports
Previous releases - always broken:
- ethtool: do not perform operations on net devices being
unregistered
- udp: use datalen to cap max gso segments
- ice: fix races in stats collection
- fec: only clear interrupt of handling queue in fec_enet_rx_queue()
- m_can: pci: fix incorrect reference clock rate
- m_can: disable and ignore ELO interrupt
- mvpp2: fix XDP rx queues registering
Misc:
- treewide: add missing includes masked by cgroup -> bpf.h
dependency"
* tag 'net-5.16-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (82 commits)
net: dsa: mv88e6xxx: allow use of PHYs on CPU and DSA ports
net: wwan: iosm: fixes unable to send AT command during mbim tx
net: wwan: iosm: fixes net interface nonfunctional after fw flash
net: wwan: iosm: fixes unnecessary doorbell send
net: dsa: felix: Fix memory leak in felix_setup_mmio_filtering
MAINTAINERS: s390/net: remove myself as maintainer
net/sched: fq_pie: prevent dismantle issue
net: mana: Fix memory leak in mana_hwc_create_wq
seg6: fix the iif in the IPv6 socket control block
nfp: Fix memory leak in nfp_cpp_area_cache_add()
nfc: fix potential NULL pointer deref in nfc_genl_dump_ses_done
nfc: fix segfault in nfc_genl_dump_devices_done
udp: using datalen to cap max gso segments
net: dsa: mv88e6xxx: error handling for serdes_power functions
can: kvaser_usb: get CAN clock frequency from device
can: kvaser_pciefd: kvaser_pciefd_rx_error_frame(): increase correct stats->{rx,tx}_errors counter
net: mvpp2: fix XDP rx queues registering
vmxnet3: fix minimum vectors alloc issue
net, neigh: clear whole pneigh_entry at alloc time
net: dsa: mv88e6xxx: fix "don't use PHY_DETECT on internal PHY's"
...
Daniel Borkmann says:
====================
bpf 2021-12-08
We've added 12 non-merge commits during the last 22 day(s) which contain
a total of 29 files changed, 659 insertions(+), 80 deletions(-).
The main changes are:
1) Fix an off-by-two error in packet range markings and also add a batch of
new tests for coverage of these corner cases, from Maxim Mikityanskiy.
2) Fix a compilation issue on MIPS JIT for R10000 CPUs, from Johan Almbladh.
3) Fix two functional regressions and a build warning related to BTF kfunc
for modules, from Kumar Kartikeya Dwivedi.
4) Fix outdated code and docs regarding BPF's migrate_disable() use on non-
PREEMPT_RT kernels, from Sebastian Andrzej Siewior.
5) Add missing includes in order to be able to detangle cgroup vs bpf header
dependencies, from Jakub Kicinski.
6) Fix regression in BPF sockmap tests caused by missing detachment of progs
from sockets when they are removed from the map, from John Fastabend.
7) Fix a missing "no previous prototype" warning in x86 JIT caused by BPF
dispatcher, from Björn Töpel.
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
bpf: Add selftests to cover packet access corner cases
bpf: Fix the off-by-two error in range markings
treewide: Add missing includes masked by cgroup -> bpf dependency
tools/resolve_btfids: Skip unresolved symbol warning for empty BTF sets
bpf: Fix bpf_check_mod_kfunc_call for built-in modules
bpf: Make CONFIG_DEBUG_INFO_BTF depend upon CONFIG_BPF_SYSCALL
mips, bpf: Fix reference to non-existing Kconfig symbol
bpf: Make sure bpf_disable_instrumentation() is safe vs preemption.
Documentation/locking/locktypes: Update migrate_disable() bits.
bpf, sockmap: Re-evaluate proto ops when psock is removed from sockmap
bpf, sockmap: Attach map progs to psock early for feature probes
bpf, x86: Fix "no previous prototype" warning
====================
Link: https://lore.kernel.org/r/20211208155125.11826-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Pull timer fix from Borislav Petkov:
- Prevent a tick storm when a dedicated timekeeper CPU in nohz_full
mode runs for prolonged periods with interrupts disabled and ends up
programming the next tick in the past, leading to that storm
* tag 'timers_urgent_for_v5.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers/nohz: Last resort update jiffies on nohz_full IRQ entry
Pull scheduler fixes from Borislav Petkov:
- Properly init uclamp_flags of a runqueue, on first enqueuing
- Fix preempt= callback return values
- Correct utime/stime resource usage reporting on nohz_full to return
the proper times instead of shorter ones
* tag 'sched_urgent_for_v5.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/uclamp: Fix rq->uclamp_max not set on first enqueue
preempt/dynamic: Fix setup_preempt_mode() return value
sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full
Commit d81ae8aac8 ("sched/uclamp: Fix initialization of struct
uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to
match the woken up task's uclamp_max when the rq is idle.
The code was relying on rq->uclamp_max initialized to zero, so on first
enqueue
static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
enum uclamp_id clamp_id)
{
...
if (uc_se->value > READ_ONCE(uc_rq->value))
WRITE_ONCE(uc_rq->value, uc_se->value);
}
was actually resetting it. But since commit d81ae8aac8 changed the
default to 1024, this no longer works. And since rq->uclamp_flags is
also initialized to 0, neither above code path nor uclamp_idle_reset()
update the rq->uclamp_max on first wake up from idle.
This is only visible from first wake up(s) until the first dequeue to
idle after enabling the static key. And it only matters if the
uclamp_max of this task is < 1024 since only then its uclamp_max will be
effectively ignored.
Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to
ensure uclamp_idle_reset() is called which then will update the rq
uclamp_max value as expected.
Fixes: d81ae8aac8 ("sched/uclamp: Fix initialization of struct uclamp_rq")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com
The first commit cited below attempts to fix the off-by-one error that
appeared in some comparisons with an open range. Due to this error,
arithmetically equivalent pieces of code could get different verdicts
from the verifier, for example (pseudocode):
// 1. Passes the verifier:
if (data + 8 > data_end)
return early
read *(u64 *)data, i.e. [data; data+7]
// 2. Rejected by the verifier (should still pass):
if (data + 7 >= data_end)
return early
read *(u64 *)data, i.e. [data; data+7]
The attempted fix, however, shifts the range by one in a wrong
direction, so the bug not only remains, but also such piece of code
starts failing in the verifier:
// 3. Rejected by the verifier, but the check is stricter than in #1.
if (data + 8 >= data_end)
return early
read *(u64 *)data, i.e. [data; data+7]
The change performed by that fix converted an off-by-one bug into
off-by-two. The second commit cited below added the BPF selftests
written to ensure than code chunks like #3 are rejected, however,
they should be accepted.
This commit fixes the off-by-two error by adjusting new_range in the
right direction and fixes the tests by changing the range into the
one that should actually fail.
Fixes: fb2a311a31 ("bpf: fix off by one for range markings with L{T, E} patterns")
Fixes: b37242c773 ("bpf: add test cases to bpf selftests to cover all access tests")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211130181607.593149-1-maximmi@nvidia.com
At CPU-hotplug time, unbind_workers() may preempt a worker while it is
going to sleep. In that case the following scenario can happen:
unbind_workers() wq_worker_sleeping()
-------------- -------------------
if (worker->flags & WORKER_NOT_RUNNING)
return;
//PREEMPTED by unbind_workers
worker->flags |= WORKER_UNBOUND;
[...]
atomic_set(&pool->nr_running, 0);
//resume to worker
atomic_dec_and_test(&pool->nr_running);
After unbind_worker() resets pool->nr_running, the value is expected to
remain 0 until the pool ever gets rebound in case cpu_up() is called on
the target CPU in the future. But here the race leaves pool->nr_running
with a value of -1, triggering the following warning when the worker goes
idle:
WARNING: CPU: 3 PID: 34 at kernel/workqueue.c:1823 worker_enter_idle+0x95/0xc0
Modules linked in:
CPU: 3 PID: 34 Comm: kworker/3:0 Not tainted 5.16.0-rc1+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (rcu_par_gp)
RIP: 0010:worker_enter_idle+0x95/0xc0
Code: 04 85 f8 ff ff ff 39 c1 7f 09 48 8b 43 50 48 85 c0 74 1b 83 e2 04 75 99 8b 43 34 39 43 30 75 91 8b 83 00 03 00 00 85 c0 74 87 <0f> 0b 5b c3 48 8b 35 70 f1 37 01 48 8d 7b 48 48 81 c6 e0 93 0
RSP: 0000:ffff9b7680277ed0 EFLAGS: 00010086
RAX: 00000000ffffffff RBX: ffff93465eae9c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9346418a0000 RDI: ffff934641057140
RBP: ffff934641057170 R08: 0000000000000001 R09: ffff9346418a0080
R10: ffff9b768027fdf0 R11: 0000000000002400 R12: ffff93465eae9c20
R13: ffff93465eae9c20 R14: ffff93465eae9c70 R15: ffff934641057140
FS: 0000000000000000(0000) GS:ffff93465eac0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001cc0c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
worker_thread+0x89/0x3d0
? process_one_work+0x400/0x400
kthread+0x162/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Also due to this incorrect "nr_running == -1", all sorts of hazards can
happen, starting with queued works being ignored because no workers are
awaken at insert_work() time.
Fix this with checking again the worker flags while pool->lock is locked.
Fixes: b945efcdd0 ("sched: Remove pointless preemption disable in sched_submit_work()")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
At CPU-hotplug time, unbind_worker() may preempt a worker while it is
waking up. In that case the following scenario can happen:
unbind_workers() wq_worker_running()
-------------- -------------------
if (!(worker->flags & WORKER_NOT_RUNNING))
//PREEMPTED by unbind_workers
worker->flags |= WORKER_UNBOUND;
[...]
atomic_set(&pool->nr_running, 0);
//resume to worker
atomic_inc(&worker->pool->nr_running);
After unbind_worker() resets pool->nr_running, the value is expected to
remain 0 until the pool ever gets rebound in case cpu_up() is called on
the target CPU in the future. But here the race leaves pool->nr_running
with a value of 1, triggering the following warning when the worker goes
idle:
WARNING: CPU: 3 PID: 34 at kernel/workqueue.c:1823 worker_enter_idle+0x95/0xc0
Modules linked in:
CPU: 3 PID: 34 Comm: kworker/3:0 Not tainted 5.16.0-rc1+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (rcu_par_gp)
RIP: 0010:worker_enter_idle+0x95/0xc0
Code: 04 85 f8 ff ff ff 39 c1 7f 09 48 8b 43 50 48 85 c0 74 1b 83 e2 04 75 99 8b 43 34 39 43 30 75 91 8b 83 00 03 00 00 85 c0 74 87 <0f> 0b 5b c3 48 8b 35 70 f1 37 01 48 8d 7b 48 48 81 c6 e0 93 0
RSP: 0000:ffff9b7680277ed0 EFLAGS: 00010086
RAX: 00000000ffffffff RBX: ffff93465eae9c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9346418a0000 RDI: ffff934641057140
RBP: ffff934641057170 R08: 0000000000000001 R09: ffff9346418a0080
R10: ffff9b768027fdf0 R11: 0000000000002400 R12: ffff93465eae9c20
R13: ffff93465eae9c20 R14: ffff93465eae9c70 R15: ffff934641057140
FS: 0000000000000000(0000) GS:ffff93465eac0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001cc0c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
worker_thread+0x89/0x3d0
? process_one_work+0x400/0x400
kthread+0x162/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Also due to this incorrect "nr_running == 1", further queued work may
end up not being served, because no worker is awaken at work insert time.
This raises rcutorture writer stalls for example.
Fix this with disabling preemption in the right place in
wq_worker_running().
It's worth noting that if the worker migrates and runs concurrently with
unbind_workers(), it is guaranteed to see the WORKER_UNBOUND flag update
due to set_cpus_allowed_ptr() acquiring/releasing rq->lock.
Fixes: 6d25be5782 ("sched/core, workqueues: Distangle worker accounting from rq lock")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Vinicius Costa Gomes reported [0] that build fails when
CONFIG_DEBUG_INFO_BTF is enabled and CONFIG_BPF_SYSCALL is disabled.
This leads to btf.c not being compiled, and then no symbol being present
in vmlinux for the declarations in btf.h. Since BTF is not useful
without enabling BPF subsystem, disallow this combination.
However, theoretically disabling both now could still fail, as the
symbol for kfunc_btf_id_list variables is not available. This isn't a
problem as the compiler usually optimizes the whole register/unregister
call, but at lower optimization levels it can fail the build in linking
stage.
Fix that by adding dummy variables so that modules taking address of
them still work, but the whole thing is a noop.
[0]: https://lore.kernel.org/bpf/20211110205418.332403-1-vinicius.gomes@intel.com
Fixes: 14f267d95f ("bpf: btf: Introduce helpers for dynamic BTF set registration")
Reported-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211122144742.477787-2-memxor@gmail.com
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime
than the actual time.
task_cputime_adjusted() snapshots utime and stime and then adjust their
sum to match the scheduler maintained cputime.sum_exec_runtime.
Unfortunately in nohz_full, sum_exec_runtime is only updated once per
second in the worst case, causing a discrepancy against utime and stime
that can be updated anytime by the reader using vtime.
To fix this situation, perform an update of cputime.sum_exec_runtime
when the cputime snapshot reports the task as actually running while
the tick is disabled. The related overhead is then contained within the
relevant situations.
Reported-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
When at least one CPU runs in nohz_full mode, a dedicated timekeeper CPU
is guaranteed to stay online and to never stop its tick.
Meanwhile on some rare case, the dedicated timekeeper may be running
with interrupts disabled for a while, such as in stop_machine.
If jiffies stop being updated, a nohz_full CPU may end up endlessly
programming the next tick in the past, taking the last jiffies update
monotonic timestamp as a stale base, resulting in an tick storm.
Here is a scenario where it matters:
0) CPU 0 is the timekeeper and CPU 1 a nohz_full CPU.
1) A stop machine callback is queued to execute somewhere.
2) CPU 0 reaches MULTI_STOP_DISABLE_IRQ while CPU 1 is still in
MULTI_STOP_PREPARE. Hence CPU 0 can't do its timekeeping duty. CPU 1
can still take IRQs.
3) CPU 1 receives an IRQ which queues a timer callback one jiffy forward.
4) On IRQ exit, CPU 1 schedules the tick one jiffy forward, taking
last_jiffies_update as a base. But last_jiffies_update hasn't been
updated for 2 jiffies since the timekeeper has interrupts disabled.
5) clockevents_program_event(), which relies on ktime_get(), observes
that the expiration is in the past and therefore programs the min
delta event on the clock.
6) The tick fires immediately, goto 3)
7) Tick storm, the nohz_full CPU is drown and takes ages to reach
MULTI_STOP_DISABLE_IRQ, which is the only way out of this situation.
Solve this with unconditionally updating jiffies if the value is stale
on nohz_full IRQ entry. IRQs and other disturbances are expected to be
rare enough on nohz_full for the unconditional call to ktime_get() to
actually matter.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20211026141055.57358-2-frederic@kernel.org
The 'kprobe::data_size' is unsigned, thus it can not be negative. But if
user sets it enough big number (e.g. (size_t)-8), the result of 'data_size
+ sizeof(struct kretprobe_instance)' becomes smaller than sizeof(struct
kretprobe_instance) or zero. In result, the kretprobe_instance are
allocated without enough memory, and kretprobe accesses outside of
allocated memory.
To avoid this issue, introduce a max limitation of the
kretprobe::data_size. 4KB per instance should be OK.
Link: https://lkml.kernel.org/r/163836995040.432120.10322772773821182925.stgit@devnote2
Cc: stable@vger.kernel.org
Fixes: f47cd9b553 ("kprobes: kretprobe user entry-handler")
Reported-by: zhangyue <zhangyue1@kylinos.cn>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The current queue_work_on() docbook comment says that the caller must
ensure that the specified CPU can't go away, but does not spell out the
consequences, which turn out to be quite mild. Therefore expand this
comment to explicitly say that the penalty for failing to nail down the
specified CPU is that the workqueue handler might find itself executing
on some other CPU.
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull scheduler fix from Thomas Gleixner:
"A single scheduler fix to ensure that there is no stale KASAN shadow
state left on the idle task's stack when a CPU is brought up after it
was brought down before"
* tag 'sched-urgent-2021-11-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/scs: Reset task stack state in bringup_cpu()
